A strain can occur as a result of improper body mechanics with any activity (e.g., contact sports, lifting heavy objects, overstretching) that can induce mechanical trauma or injury.[2] Generally, the muscle or tendon overstretches and is placed under more physical stress than it can exert.[2] Strains commonly result in a partial or complete tear of a tendon or muscle, or they can be severe in the form of a complete tendon rupture.[5] The most common body location for strains to occur is in the foot, leg, or back.[5]

Acute strains are more closely associated with recent mechanical trauma or injury.

Chronic strains typically result from repetitive movement of the muscles and tendons over a long period of time.[2]

Degrees of Injury (as classified by the American College of Sports Medicine):[6]

Although strains are not restricted to athletes and can happen while doing everyday tasks, people who play sports are more at risk for developing a strain.[5] It is common for an injury to develop when there is a sudden increase in duration, intensity, or frequency of an activity.[5]

A new treatment for acute strains is the use of platelet rich plasma (PRP) injections which have been shown to accelerate recovery from non surgical muscular injuries.[16]

It is recommended[17] that the person injured should consult a medical provider if the injury is accompanied by severe pain, if the limb cannot be used, or if there is noticeable tenderness over an isolated spot. These can be signs of a broken or fractured bone, a sprain, or a complete muscle tear.